Article Including a Heat-Stable Coating Provided with an at Least Two-Color Decoration Having Continuous Tones, and Method for Manufacturing Such an Article

ABSTRACT

The present invention relates to a heating article ( 1 ) which includes a substrate ( 2 ) having two opposite surfaces ( 21, 22 ), at least one of which is opaque, and a heat-stable coating ( 3 ) arranged on said opaque surface ( 21 ). According to the invention, the heat-stable coating ( 3 ) includes an at least two-colour decoration ( 31 ) having continuous tones and being provided in the form of a continuous or discontinuous layer, and the heating article has been cured at a temperature of more than 300° C. The present invention also relates to a method for manufacturing such an article ( 1 ).

The present invention relates to an article comprising a heat-stablecoating provided with an at least two-color decoration and method formanufacturing such an article. The present invention also relates to amethod for manufacturing such articles, wherein the decoration isapplied by ink jet printing.

Several types of techniques are known for decorating a culinary article.

Particularly, it is known by the skilled person to use screen printingor tamp print techniques in order to apply patterns on flat surfaces todecorate them. These techniques allow for a shaping operation of thearticle achieved following the application of patterns by screenprinting or tamp print.

If screen printing is used (or tamp print) to apply multicoloredpatterns, several screen printing (or tamp print) operations should thenbe carried out one after the other according to the number of colors:each color requiring a pass of screen time (or tamp print), consideringthat each print must be followed by a drying operation before printingthe following layer of ink. Such a printing technique is only profitablewhen the same image or pattern is applied on a large number of supports.For printing a small number of pieces, a screen print (or tamp print) inseveral colors is very expensive and is certainly not profitable in asfar as a separate screen (or engraved print) is necessary for each basecolor. Furthermore, the cost of making and cleaning of the printingscreen is high, the time it takes to realize the screen is long thus,requiring flawless planning of the productions. Furthermore, the changeof tint although it is achieved in an identical style requires neatcleaning which reduces the production time. (Likewise for the engravedprint). Furthermore, the screen print and tamp print techniques generateimportant stocks of products and intermediary products (particularlyinks, screens, half-finished bowls, etc).

It is also known to use the printing technique by sublimation in orderto obtain a decorated culinary article. Generally, the sublimation isthe transformation of a solid body into gas or vapor, without goingthrough a liquid stage. According to the sublimation printing technique,the pattern initially printed on a support (paper of plastic film) ispressed flat against the surface of the article to be decorated, thenthe whole is briefly taken to a temperature between 150° and 210° C. Thetraditional sublimation printing is only used on flat-shaped articlesbecause the pressure of the support on an article of non-flat shaperesults in its creasing and consequently results in printing flaws.However, it is known, by referenced documents EP 0451067 and EP 544 603,improvements of the sublimation printing method which make it possibleto decorate all the sides of an article of any shape whatsoever.However, such improvements make printing methods by sublimation verycomplex to implement and hardly productive.

Furthermore, and as illustrated on FIG. 8, it is known to use a printingtechnique called ink-jet which consists in projecting droplets of inkfrom a small opening to perfectly determined positions on a support,such as to create an image. The ink-jet printing is the only contactlessprinting technique. Two types of ink-jet printing techniques aredistinguishable: the first is called “continuous ink jet” correspondingto its abbreviation CIJ and the second is called “drop on demand”corresponding to abbreviation DOD.

The ink-jet printing technique intrinsically has advantages which,parallel to the development of IT tools and to an increase in thequality and printing speeds, explain its success. On the one hand, theabsence of a printing form (screen, engraved print) eliminates thepreparation work that is necessary for the implementation of otherprinting techniques, particularly the preparation of the screens, theengraving of the prints or, where necessary, the supports (paper orplastic film). On the other hand, the dynamic management of the printingdata, which more particularly vary with each page to be printed, makesit possible to personalize documents and allow for the print run of verysmall series without incurring unacceptably high costs.

Apart from office work and the personalization of documents, theapplications of ink jet printing are multiple: posters in large and verylarge format, printing on textiles, ceramic decoration, labeling,addressing, printing on food, deposit of active principles, deposit ofbiomaterials, conductive ink printing, etc.

Among the applications of the ink jet printing technique, oneapplication relates to the decoration of articles whereof themanufacturing method requires high temperature curing. These articlesare more particularly ceramic squares. In the field of manufacturingceramic articles, the manufacturing techniques, for example sintering orthe fusion of powders, bring the articles to temperatures of at least300° C. that can reach 1300° C. and beyond. Thereby, it is not possibleto print decorations according to the ink jet technique by usingstandard inks such as used in paper or textile printing. Special inks,but also printing heads and adapted software have been developed. It iscited, for example, the QuickPaint® inks and the KERAJET printeraccording to their respective commercial name.

In the field of culinary articles exhibiting a decoration printed by inkjet, document JP05049541 teaches a stratified material comprising asubstrate, a first layer to ensure the adhesion with the substrate, aprinting layer deposited on the first layer and an upper layerconsisting in a fluoro-resin deposited on the printing layer. Thismaterial solves the problem of localized engraving, for example capacityengraving, for which pre-existent solutions were based on a mechanicalengraving (reliefs) which weakened the coating (fast wear). Furthermore,the decoration of the material JP 05049541 is monochrome and composed ofthe combination of points having a surface of approximately 2 mm².Nothing is said in JP 05049541 as regards a decoration comprisingseveral colors.

It is further known by the Korean patent application KR2007/0117247 amethod of ink jet printing of patterns on the surface of a culinaryarticle covered beforehand by a white opaque sub-layer, whereon isdeposited an organic transparent ink receiving layer, involving athinner and a hardener of organic nature in order to allow for a goodadhesion of the projected ink. After printing the patterns on thereceiving layer, a protective coating layer is applied on the printedpatterns, then undergoes a curing at a temperature lower than 300° C.

However, in order to obtain coatings of heating articles exhibitingsatisfactory functional properties, (particularly in terms ofanti-adhesion for PTFE-based coatings or in terms of shine and hardnessfor enameled coatings), the composition of the protective coating layerrequires for its solidification a curing temperature higher than 300° C.In fact, such a temperature is necessary in order to obtain afluorocarbon resin-based sintered coating (for example PTFE) orvitrified (in the case of an enameled coating).

However, with such conditions of implementation, it is not to beconsidered to achieve a coating comprising an organic ink receivinglayer, a decoration layer obtained by ink jet printing and afluorocarbon resin based or vitrified sintered protective coating layer(in the case of an enamel). In fact, during curing (at a temperaturehigher than 300° C.), the organic components of the receiver layerbecome degraded and are trapped by the finishing layer, thus causing atanning of the coating and hides the patterns.

In order to resolve this issue, the applicant has discovered that it waspossible to do without the ink receiving layer by depositing by ink jetprinting a composition of decoration directly on an opaque side of asupport (for example of a metal hollow bowl of a culinary article).

By opaque side, is meant, as defined by the present invention, a sidethat is intrinsically opaque by the nature of the constitutive materialof the support, or which has become opaque by covering by a continuousopaque sub-layer.

By way of examples of intrinsically opaque materials, is meant, asdefined by the present invention aluminum or aluminum alloys, magnesiumor magnesium alloys, stainless steels, cast irons, copper, titanium andmore generally metals and metallic alloys, ceramics (porcelain, faienceand more generally culinary pottery), where the composite materialscomprise a plurality of layers of one or several of the previousmaterials (in this instance co-laminated metals)

By opaque sub-layer, is meant, as defined by the present invention, alayer of material comprising a chemical substance optically nontransparent, for example a substance chosen among the heat-stable orthermochromic pigments, the colored or metal flakes, the opacifyingfillers and their combinations.

The opaque sub-layer is preferably pigmented, and better if it is ablack or a white color, and even better if white.

The adhesion of the “ink jet” decoration thus formed on the support isensured:

-   -   either by superficial absorption thanks to the porosity of the        support itself of the sub-layer if need be,    -   or thanks to the composition of the ink of the ink jet        decoration which comprises a binder.

More particularly, the purpose of the present invention is a heatingarticle comprising a substrate having two opposite sides, whereof one isat least opaque, and a heat-stable coating arranged on said opaque side.

According to the invention, the heat-stable coating comprises adecoration of at least two colors in continuous tones in the form of acontinuous or discontinuous layer, and the heating article has beensubjected to a curing at a temperature higher than 300° C.

By decoration in continuous tones, is meant, as defined by the presentinvention, a decoration which can comprise all the shades between thelightest tones and the darkest ones, without points appearing, which isdifferent from a decoration in direct tone or in color block resultingin a high contrast, such as for example the decoration described ininternational patent WO2008/142327 belonging to the present applicant.

By heating article, is meant, as defined by the present invention anarticle having its own heating system, or which is heated by an outersystem and which is able to transmit the calorific energy brought bythis system to a third material or object in contact with said article.

If the substrate is not intrinsically opaque, it is indispensable torecover beforehand the side to be decorated by an opaque sub-layer, onwhich the decoration is printed. An appropriate sub-layer is such asdescribed previously and exhibits the aforementioned properties.

According to a first embodiment of the heating article according to theinvention, the decoration is exempt from binders. In this case, theadhesion of the decoration to the support is ensured by the porosity ofthe support or of the sub-layer, if need be, by superficial absorptionof the decoration. Advantageously, the support or the sub-layer that iscovered by the decoration exempt from binders is not smooth and has asuperficial roughness Ra lower or equal to 10 μm.

According to a second embodiment of the heating article according to theinvention, the decoration comprises at least a heat-stable bindercompatible with the substrate and/or, if need be with the sub-layer. Inthis case, the adhesion of the decoration to the support is ensured bythe binder of the composition of the decoration. It is thus, notnecessary that the support be porous.

By heat-stable binder, is meant, as defined by the present invention, aheat-stable binder at, at least 300° C.

By way of heat-stable binder usable in the layer of decoration accordingto the invention, one may particularly cite enamels, fluorocarbon resins(alone or in combination), inorganic polymers or organic-inorganichybrids synthesized by sol-gel process, silicones, silicon-polyesters,polyimids, polyphenylene sulfide (PPS), ethylene sulphide polymer (PES),polyetheretherketones (PEEK), polyetherketones (PEK), polyamids-imids(PAI) silicones, fluorosilicones, polybenzimidazoles (PBI), consideringthat these materials must be finely dispersible or solubilizable in thecomposition of the decoration.

The heat-stable coating according to the invention may further comprisea continuous finishing layer. It can be deposited on the decoration, andis necessarily transparent such as not to conceal the decoration.

By transparent coating (whether it be particularly sol-gel coating orthe finishing layer), is meant, as defined by the present invention, acoating letting all or part of the decoration be visible.

This finishing layer may also be disposed between the support or thesub-layer (if need be) and the decoration. In this last case, it is notnecessary that the finishing layer be transparent since the decorationcovers the finishing layer, as illustrated by FIG. 7 hereinafter.

If the decoration comprises a heat-stable binder, the latter must notonly be compatible with the substrate and/or, if need be with thesub-layer, but also with the finishing layer.

The decoration of the heat-stable coating according to the invention isa two-tone decoration, that is to say, that it comprises at least twodifferent color compounds. These may be chosen among the heat-stablepigments, metal salts, semi-conductive thermochromic pigments,conductive pigments, magnetic pigments and their combinations.

The decoration according to the invention is advantageously ahyper-realistic decoration which very precisely reproduces thedecoration chosen beforehand that is sought to be printed. According toa particularly advantageous embodiment of the present invention, thedecoration according to the invention is at least four-color andpreferably hexachrome.

It is considered different types of articles conform to the invention,of different shapes and achieved in various materials.

Thus, the support may be in a material chosen among metals, glass,ceramics and plastic materials.

By way of metal supports usable in the method of the invention, one mayadvantageously cite aluminum or aluminum alloy supports anodized or not,or in polished, brushed, microbeaded or sanded aluminum, treatedchemically or in polished, brushed or microbeaded stainless steel, or incast iron or aluminum, in titanium or in polished or beaten copper.

The heating article according to the invention may particularly be aculinary article, and in particular a culinary article whereof one ofthe opposite sides is a concave inner side intended to be arranged onthe side of the foods liable to be introduced in said article, and asecond of said opposite sides is an outer convex side intended to bearranged towards a heat source.

By way of non-limiting examples of culinary articles conforming to thepresent invention, will be particularly cited culinary articles such aspans and frying pans, woks and fryers, stewpots and pots, crepe pans,grills, molds and baking plates, plates and barbecue grills, preparationbowls.

Other types of supports can also be considered, not limited to the soleculinary field. Thus, one may also consider by way of articles conformwith the invention household appliances such as irons, curling irons,hair straighteners etc., isothermal pots (for coffee machines forexample) or mixing bowls.

In the case where the heating article according to the invention is aculinary article such as described above, the decoration isadvantageously presented in the form of a continuous or discontinuouslayer, which may be arranged either on the inner side of the article, oron its outer side. As previously indicated, the decoration may either beexempt from binders or comprise a heat-stable binder.

If the decoration is arranged on the inner side of the culinary article,the heat-stable binder will be preferably chosen among fluorocarbonresins, inorganic polymers or organic-inorganic hybrids synthesized bysol-gel process, polyphenylene sulfide (PPS), ethylene sulphide polymer(PES), polyetheretherketones (PEEK), polyetherketones (PEK),polyamids-imids (PAI), polybenzimidazoles (PBI).

If the decoration is arranged on the outer side of the culinary article,the heat-stable binder will be preferably chosen among enamels,fluorocarbon resins (alone or in combination), inorganic polymers ororganic-inorganic hybrids synthesized by sol-gel process, silicones,silicone-polyesters, polyimids, polyphenylene sulfide (PPS), ethylenesulphide polymer (PES), polyetheretherketones (PEEK), polyetherketones(PEK), polyamids-imids (PAI), silicones, fluorosilicones,polybenzimidazoles (PBI).

By way of non-limiting examples of culinary articles conform with thepresent invention, it is particularly cited culinary articles such aspans and frying pans, woks and fryers, crepe pans, grills, molds andbaking plates, plates and barbecue grills.

The present invention also relates to a method for manufacturing aheating article including the following steps:

-   -   a) providing of a substrate comprising two opposite sides,        whereof one is at least opaque or made opaque; then    -   b) achieving a heat-stable coating on said opaque side, which        comprises the following steps:        -   b1) a step of applying on said opaque side of a composition            of decoration, to form a moist layer of decoration covering            at least partially said opaque side; then        -   b2) a heat treatment of solidifying said moist layer of the            decoration, to form a decoration having the form of a            continuous or discontinuous layer covering at least            partially said opaque side.

According to the invention, the composition of the layer of decorationcomprises at least two different color compounds and is applied by inkjet printing, and the heat treatment of solidifying the moist layer ofdecoration is achieved at a temperature equal to or higher than 300° C.

The substrate, the layer of decoration and the color compounds that itcontains are such as defined previously.

If the substrate is not intrinsically opaque, it is indispensable tocover beforehand the side to be decorated by an opaque sub-layer, onwhich the decoration is printed. Such a sub-layer is such as describedpreviously and has the above mentioned properties.

The opaque surface of the substrate (intrinsically opaque or madeopaque) may relate to a step of preparation such as for exampledegreasing, abrasive blasting, shot-peening, brushing, grinding,satin-finishing, chemical etching, anodization.

The method according to the invention may further comprise a step ofachieving a finishing layer. This step may be carried out by applying acontinuous and transparent finishing composition (for the same reasonsas those mentioned beforehand) on the moist layer of decoration obtainedfollowing the step b1), prior to the heat treatment b2) ofsolidification. The step of achieving the finishing layer may also beachieved by applying a continuous finishing layer composition (notnecessarily transparent), prior to carrying out b1) of the decorationlayer (31).

As aforementioned, the decoration composition can or cannot comprise aheat-stable binder: according to the porosity of the substrate or of theunderlying sub-layer, the presence of this heat-stable binder will orwill not be indispensable (it is indispensable in the case of a smoothsubstrate). The nature of the heat-stable binder is such asaforementioned.

Other advantages and features of the present invention will result fromthe following description, given by way of non-limiting example and madewith reference to the accompanying drawings:

FIG. 1 represents a cross-sectional schematic view of a culinary articlethat conforms with the invention according to a first embodiment,

FIG. 2 represents a cross-sectional schematic view of a support ofculinary article that conforms with the invention according to thesecond embodiment,

FIGS. 3 to 7 represent cross-sectional schematic views of a portion ofthe base of a culinary article comprising a heat-stable coatingaccording to the invention, according to different alternativeembodiments,

FIG. 8 represents a cross-sectional schematic view of an industrialdevice for ink jet decorating.

The identical elements represented on FIGS. 1 to 7 are identified byidentical numerical references.

On FIGS. 1 and 2, it has been represented, by way of example of aculinary article according to the invention, a frying pan 1 comprising asupport 2 having the form of a hollow bowl with a base 24 and a lateralwall 25 rising from the base 24, and a grip handle 5. The support 2comprises an inner concave side 21 able to receive food, and an outerconvex side 22 intended to be arranged on the side of the heat source,such as a cooking plate or a burner.

On FIG. 1, the inner side 21 of the support 2 is covered by aheat-stable coating 3 according to the invention. However, on FIG. 2, itis the outer side 22 of the support 2 which is covered by a heat-stablecoating 3 according to the invention.

The different alternative embodiments of the heat-stable coating 3according to the invention represented on FIGS. 1 and 2 are illustratedin a detailed manner by FIGS. 3 to 7. They correspond to top views ofthe base 24 of the heating article 1 represented on FIG. 1 (heat-stablecoating 3 with decoration 31 on the inner side 21), or to bottom viewsof the base of the article represented on FIG. 2 (heat-stable coating 3with decoration 31 on the outer side 22):

-   -   on FIG. 3, the heat-stable coating 3 is only constituted of the        decoration 31 (continuous portion on FIG. 3), which is directly        arranged on the support 2, that is to say:        -   either directly on the inner side 21 in the case of the            embodiment illustrated on FIG. 1; in this case, FIG. 3 is a            top view of the base of the article 1,        -   or directly on the outer side 22 in the case of the            embodiment illustrated on FIG. 2; in this case, FIG. 3 is a            top view of the base of the article 1;    -   FIG. 4 differs from FIG. 3 by the presence of a continuous and        transparent finishing layer 32 arranged on the decoration 31;    -   FIG. 5 differs from FIG. 3 by the presence of an opaque        sub-layer 4, between the decoration 31 and the support 2, that        is to say the inner side 21 for the embodiment illustrated on        FIG. 1 (top view) or the outer side 22 for the embodiment        illustrated on FIG. 2 (bottom view),    -   FIG. 6 differs from FIG. 5 by the presence of a continuous and        transparent finishing layer 32 arranged on the decoration 31 on        FIG. 6,    -   FIG. 7 differs from FIG. 5 by the presence of a continuous        finishing layer 32 arranged between the sub-layer 4 and the        decoration (31).

The compositions of the decoration 31 and finishing layers, as well asthe heat-stable binder of these layers (if need be) are such asdescribed beforehand.

On FIG. 8, is represented a cross-sectional schematic view of anindustrial device for ink jet decorating operating according to the“drop on demand” technology “DOD”. The operating of this device is thatdescribed in international patent WO 2006/126189. It consists in apiezoelectric DOD-type method, for which the drops required for printingare created by the deformation of the wall of the ink container, as aresult of an electrical excitation of a piezoelectric crystal.

The invention is illustrated in further detail in the followingexamples.

In these examples, except otherwise indicated, all percentages andportions are expressed in weight.

EXAMPLES (DOD) Operating Ink Jet Decorating Device

As printing device, a printer commercialized by KERAJET is used, forexample using a printer of commercial reference 700×, usually intendedfor the printing of ceramic squares.

Products Supports:

Aluminum disks with a diameter of 31 cm and a thickness of 2.4 mm.

Inks: Inks for Ink Jet Printing on Heat-Stable Coating of Ceramic Type(Enamel or Sol-Gel)

-   -   blue-colored inks commercialized by company FERRO CORPORATION        under trade names QuickPaint inks or KeramInks,    -   orange-colored inks commercialized by company FERRO under trade        names QuickPaint inks or KeramInks,    -   brown-colored inks commercialized by company FERRO under trade        names QuickPaint inks or KeramInks,    -   yellow-colored inks commercialized by company FERRO under trade        names QuickPaint inks or KeramInks,    -   pink-colored inks commercialized by company FERRO under trade        names QuickPaint inks or KeramInks,    -   black-colored inks commercialized by company FERRO under trade        names QuickPaint inks or KeramInks.

Pigmented Aqueous Inks for Ink Jet Printing on Non-Enameled Heat-StableCoatings

It consists of aqueous formulations adapted for ink jet printing such asknown by the skilled person. These formulations contain inorganicpigments allowing for a good hold in temperature of the colors, water asa main vehicle with at least a co-solvent and at least a dispersant toenable a good stability of the pigments in suspension.

The choice of pigments could be done as follows:

-   -   for blue ink, a cobalt blue will be for example taken (Color        index PB28),    -   for the red, a red iron oxide (Color index PR101),    -   for the yellow, a yellow iron oxide (Color index PY42), and    -   for the black, a carbon black (Color index PBk7). These inks are        prepared as follows:

1/ Preparation of a Pigment Paste

First, a pigment paste corresponding to each color is prepared. Itconsists in a dispersion comprising between 10 and 70% of pigment, 30 to90% water and 0.1 to 10% of a dispersant (for example Disperbyk 192).This dispersion is prepared in a crusher (for example the marble crusherof LMZ type commercialized by the Netzsch GmbH company) making itpossible to reduce the granulometry of the pigments such that all theparticles be of size lower than 500 nanometers, or that this maximumsize may be easily attained by a step of filtration, so as not to riskblocking the nozzles of the printing head.

2/ Preparation of the Aqueous Ink

A standard formula ejectable by ink jet may be composed as follows:

-   -   2 to 50% pigment paste    -   20 to 70% water    -   10 to 80% solvents making it possible to adjust the viscosity        and the surface tension of the formula: for example a mixture of        glycerol/ethylene glycol with a ration ranging between 1 and 5.        The viscosity of the final ink should range between 5 and 20 cP        at its temperature of use (temperature in the printing head, for        example ranging between the ambient temperature and 40° C.) and        its superficial tension will range between 22 and 40 mN/m.

Enamel Heat-Stable Coating

A first fritted white enamel barbotine B1 is prepared based on frittedwhite enamel F1, whereof the composition is given in table 1 below:

TABLE 1 Formula of the frit for white enamel F1 Oxide of Parts in weightvariation Na 24.57 20-35 Si 40.67 32-48 K 18.33 13-23 V 7.60  0-12 Sb4.38 0-8 BA 4.45 0-6 Total 100 20-35

The composition of barbotine B1 is given herebelow:

-   -   Frit F1: 100 parts in weight,    -   Boric acid: 3 parts in weight,    -   Potash: 1.5 parts in weight,    -   Titanium dioxide: 20 parts in weight,    -   Water: 55 parts in weight.

A second finishing fritted enamel barbotine B2 is prepared from afinishing fritted enamel F2, whereof the composition is given in table 2herebelow:

TABLE 2 Formula of the finishing enamel frit F2 Oxide of Parts in weightvariation Na 21.01 15-30 Si 35.86 20-45 K 16.49 10-20 Ti 21.17 15-25 V5.47  0-10 Total 100

The composition of the barbotine B2 is given herebelow:

-   -   Frit F2: 100 parts in weight,    -   Boric acid: 3 parts in weight,    -   Potash: 1 part in weight,    -   Water: 52 parts in weight.

PTFE-Based Fluorocarbon Heat-Stable Coating

A first white polytetrafluoroethylene-based screen printing paste PS1 isprepared of which the composition is given herebelow:

-   -   PTFE dispersion at 60% dry matter and of average particle size        of 220 nm: 50%    -   water: 10%    -   pigment paste TiO₂: 20% [TiO2 pigment/water 50:50]    -   propylene glycol: 15%    -   acrylic thickener such as those commercialized by PolymerLatex        GmbH: 3%    -   ammonia: 2%

A second colorless polytetrafluoroethylene-based screen printing pastePS2 is prepared of which the composition is given herebelow:

-   -   PTFE dispersion at 60% dry matter and particle size of 220 nm:        80%    -   water: 2%    -   propylene glycol: 15%    -   acrylic thickener such as those commercialized by

PolymerLatex GmbH: 3%

-   -   ammonia: 1%

Sol-Gel Heat-Stable Coating

A sol-gel composition SG1 is prepared based on a mixture of TEOS(tetraethoxysilane) and MTMS (methyltrimethoxysilane) in alkaline mediumcontaining titanium dioxide as white pigment. A composition is givenherebelow:

-   -   20% to 40% in weight of tetraethoxysilane (TEOS);    -   40% to 50% in weight of methyltrimethoxysilane (MTMS);    -   2 l to 4 l of silica sol, with a SiO₂ content, between 10% and        40%;    -   0% to 40% in weight of micronized SiO₂ particles;    -   0% to 5% in weight of Boron trimethoxide (TMB);    -   0% to 5% in weight of sodium ethoxide;    -   0% to 5% in weight of potassium ethoxide;    -   0% to 5% in weight of sodium formate;    -   0% to 5% in weight of potassium formate;    -   0% to 5% in weight of aluminum acetylacetonate;    -   20% to 50% in weight of ethanol, propanol, butylglycol, or        hexylene glycol;    -   0% to 10% in weight of sodium hydroxide;    -   0% to 5% in weight of stabilizers, surface modifiers,        rheological additives;    -   6% to 12% in weight of TiO2 as pigment.

The indicated mass percentages are such with respect to the total weightof the sol-gel composition.

Example 1

Culinary Article in Aluminum with an Outer Enamel Coating on which isPrinted a Hyper-Realistic Decoration in Continuous Tones at the Base.

Based on an aluminum disk, a press makes it possible to obtain a bowl 2in the shape of a frying pan (flat base with skirt such as illustratedon FIGS. 1 and 2).

This bowl 2 is degreased beforehand in an alkaline solution.

The aqueous barbotine B1 is applied by spraying it on the entirety ofthe outer side in order to obtain a non cured white enamel layer 3. Astep of drying makes it possible to obtain the biscuit enamel 3.

By ink jet, is printed, by means of the device illustrated on FIG. 8, ahyper-realistic decoration 31 on the base 24 of the bowl 2 covered withbiscuit 3.

The printer by brand KERAJET® makes it possible to reproduce thedecoration in a hyper-realistic manner by hexachrome process based onsix inks of different colors for heat-stable coatings of ceramic typesuch as those described beforehand, preferably, of the same brand.

The thus, enamel-coated 3 bowl 2 provided with the hyper-realisticdecoration 31 then undergoes a heat treatment of curing at a temperatureof 560° C. during 15 minutes, after which an enamel coating is obtainedwith a very consistent reproduction of the decoration chosen on theentire flat portion of the article (base), this decoration growing paleron the skirt.

The totality of the thus, formed coating 3 retains all thecharacteristics of an even enameled coating: shine, hardness,choc-resistance, flame-resistance, resistant to the corrosion ofdetergents used in dish-washers.

The configuration of the thus, obtained coating 3 corresponds to that ofFIG. 5.

Example 2

Culinary Article in Aluminum with an Outer Enamel Coating on which isPrinted a Hyper-Realistic Decoration in Continuous Tones at the Base.

Based on an aluminum disk, a press makes it possible to obtain a bowl 2in the shape of a frying pan (flat base with skirt such as illustratedon FIGS. 1 and 2).

This bowl 2 is degreased beforehand in an alkaline solution.

The aqueous barbotine B1 is applied by spraying it on the entirety ofthe outer side in order to obtain a non cured white enamel layer 3. Thefinishing barbotine B2 is applied by spraying. A step of drying makes itpossible to obtain the biscuit enamel 3.

By ink jet, is printed, by means of the device illustrated on FIG. 8, ahyper-realistic decoration 31 on the base 24 of the bowl 2 covered withbiscuit 3.

The printer by brand KERAJET® makes it possible to reproduce thedecoration in a hyper-realistic manner by hexachrome process based onsix inks of different colors for heat-stable coatings of ceramic typesuch as those described beforehand, preferably, of homogenous brand.

The thus, enamel-coated 3 bowl 2 provided with the hyper-realisticdecoration 31 then undergoes a heat treatment of curing at a temperatureof 560° C. during 15 minutes, after which an enamel coating is obtainedwith a very consistent reproduction of the decoration chosen on theentire flat portion of the article (base), this decoration growing paleron the skirt.

The totality of the thus, formed coating 3 retains all thecharacteristics of an even enameled coating: shine, hardness,choc-resistance, flame-resistance, resistant to the corrosion ofdetergents used in dish-washers.

The configuration of the thus, obtained coating 3 corresponds to that ofFIG. 7.

Example 3

Culinary Article in Aluminum with an Outer Enamel Coating on which isPrinted a Hyper-Realistic Decoration in Continuous Tones at the Base.

Based on an aluminum disk, a press makes it possible to obtain a bowl 2in the shape of a frying pan (flat base with skirt such as illustratedon FIGS. 1 and 2).

This bowl 2 is degreased beforehand in an alkaline solution thensatin-finished in order to give a white-colored homogenous surface.

The aqueous barbotine B2 is then applied by spraying it on the entiretyof the outer side in order to obtain a non cured enamel layer 3. A stepof drying makes it possible to obtain the biscuit enamel 3.

By ink jet, is printed, by means of the device illustrated on FIG. 8, ahyper-realistic decoration 31 on the base 24 of the bowl 2 covered withbiscuit 3. The printer by brand KERAJET® makes it possible to reproducethe decoration in a hyper-realistic manner by hexachrome process basedon six inks of different colors for heat-stable coatings of ceramic typesuch as those described beforehand, preferably, of the same brand.

The thus, enamel-coated 3 bowl 2 provided with the hyper-realisticdecoration 31 then undergoes a heat treatment of curing at a temperatureof 560° C. during 15 minutes, after which an enamel coating is obtainedwith a very consistent reproduction of the decoration chosen on theentire flat portion of the article (base), this decoration growing paleron the skirt.

The totality of the thus, formed coating 3 retains all thecharacteristics of an even enameled coating: shine, hardness,choc-resistance, flame-resistance, resistant to the corrosion ofdetergents used in dish-washers.

The configuration of the thus, obtained coating 3 corresponds to that ofFIG. 5 (but by replacing the sub-layer by the finishing layer).

Example 4

Culinary Article in Aluminum with an Outer PTFE Coating on which isPrinted a Hyper-Realistic Decoration in Continuous Tones.

An aluminum disk is treated beforehand either in a chemical or amechanical manner such as to bring a surface roughness allowing for goodadhesion.

The white screen printing paste PS1 is applied by screen printing on theentirety of one of the sides in order to obtain a white, non cured PTFElayer of coating 3. This layer of coating may possibly be dried for afew minutes or may be used without a step of drying. In the event ofdrying, a cooling device makes it possible to present the disk under theprinting head at a temperature below 40° C. in order to prevent the inkfrom drying under the nozzles.

By ink jet, is printed, by means of the device illustrated on FIG. 8, ahyper-realistic decoration 31 on the side 24 of the aluminum diskcovered with the white layer 3. The printer by brand KERAJET® makes itpossible to reproduce the decoration in a hyper-realistic manner byfour-color process based on four aqueous pigmented inks such as thosedescribed beforehand.

The disk thus coated with the PTFE-based formula is provided with thehyper-realistic decoration 31 then undergoes a heat treatment of curingat a temperature of 420° C. during 10 minutes, after which a PTFEcoating is obtained with a very consistent reproduction of the chosendecoration. The disk is then stamped by the press such as to obtain abowl 2 in the shape of frying pan (flat base with skirt such asillustrated on FIGS. 1 and 2).

The thus, treated decoration 31 has excellent adhesion on the whitesub-layer 3.

The totality of the thus, formed coating 3 retains all thecharacteristics of an even PTFE coating: anti-adhesion, chemicalresistance, flame-resistance, resistant to the corrosion of detergentsused in dish-washers.

The configuration of the thus, obtained coating 3 corresponds to that ofFIG. 5.

Example 5

Culinary Article in Aluminum with an Outer PTFE Coating on which isPrinted a Hyper-Realistic Decoration in Continuous Tones.

An aluminum disk is treated beforehand either in a chemical or amechanical manner such as to bring a surface roughness allowing for goodadhesion.

The white screen printing paste PS1 is applied by screen printing on theentirety of one of the sides in order to obtain a white, non cured PTFElayer of coating 3. A step of drying between 70° and 120° C. makes itpossible to obtain the sub-layer 3. A cooling device makes it possibleto present the disk under the printing head at a temperature below 40°C. in order to prevent the ink from drying under the nozzles.

By ink jet, is printed, by means of the device illustrated on FIG. 8, ahyper-realistic decoration 31 on the side 24 of the aluminum diskcovered with the white layer 3. The printer by brand KERAJET® makes itpossible to reproduce the decoration in a hyper-realistic manner byfour-color process based on the four aqueous pigmented inks such asthose described beforehand.

Then, the colorless screen printing paste PS2 is applied such as toentirely cover the decorated sub-layer 3.

The disk thus coated in PTFE-based formulation 3 is provided with thehyper-realistic decoration 31 then undergoes a heat treatment of curingat a temperature of 420° C. during 10 minutes, after which a PTFEcoating is obtained with a very consistent reproduction of the chosendecoration. The disk is then stamped by the press such as to obtain abowl 2 in the shape of frying pan (flat base with skirt such asillustrated on FIGS. 1 and 2).

The totality of the thus, formed coating 3 retains all thecharacteristics of an even PTFE coating: anti-adhesion, chemicalresistance, flame-resistance, resistant to the corrosion of detergentsused in dish-washers.

The configuration of the thus, obtained coating 3 corresponds to that ofFIG. 6.

Example 6

Culinary Article of Glass with an Outer Sol-Gel Coating on which isPrinted a Hyper-Realistic Decoration at the Base.

One starts with a circular glass bowl 2 having the shape of an oven dishthat is degreased through alkaline process.

The sol-gel composition SG1 is applied on the outer side of thesubstrate. Then, it is dried at 100° C. by making sure to keep a notentirely cross-linked film.

Then, by ink jet, is printed, by means of the device illustrated on FIG.8, a hyper-realistic decoration 31 on the base 24 of the bowl 2 coveredin the dried sol-gel composition 3. The printer by brand KERAJET® makesit possible to reproduce the decoration in a hyper-realistic manner byhexachrome process based on six different-colored inks for heat-stablecoatings of ceramic-type such as described beforehand, preferably of thesame brand.

The thus, sol-gel coated 3 bowl 2 is provided with the hyper-realisticdecoration 31 and then undergoes a heat treatment of curing at atemperature of 450° C. during 120 minutes, after which a coating with avery consistent reproduction of the chosen decoration is obtained on theentire flat portion of the article (base), this decoration growing paleron the skirt.

The totality of the thus, formed coating 3 retains all thecharacteristics of an even sol-gel coating: shine, hardness,choc-resistance, flame-resistance, resistance to the corrosion ofdetergents used in dish-washers.

The configuration of the thus, obtained coating 3 corresponds to that ofFIG. 5.

Example 7

Culinary Article of Glass with an Outer Sol-Gel Coating on which isPrinted a Hyper-Realistic Decoration at the Base.

One starts with a circular glass bowl 2 having the shape of an oven dishthat is degreased through alkaline process.

The composition SG1 is applied on the outer side.

After applying the SG1 composition, it is dried at 100° C. by makingsure to keep a non entirely cross-linked film. A cooling device makes itpossible to present the glass bowl under the printing head at atemperature below 40° C. in order to prevent the ink from drying underthe nozzles.

Then, by ink jet, is printed, by means of the device illustrated on FIG.8, a hyper-realistic decoration 31 on the base 24 of the bowl 2 coveredwith the dried sol-gel composition 3. The printer by brand KERAJET®makes it possible to reproduce the decoration in a hyper-realisticmanner by hexachrome process based on 4 aqueous pigmented inks chosenamong the aforementioned inks.

The thus, sol-gel coated 3 bowl 2 is provided with the hyper-realisticdecoration 31 and then undergoes a heat treatment of curing at atemperature of 300° C. during 15 minutes, after which a coating with avery consistent reproduction of the decoration chosen is obtained on theentire flat portion of the article (base), this decoration growing paleron the skirt.

The totality of the thus, formed coating 3 retains all thecharacteristics of an even sol-gel coating: shine, hardness,choc-resistance, flame-resistance, resistance to the corrosion ofdetergents used in dish-washers.

The configuration of the thus, obtained coating 3 corresponds to that ofFIG. 5.

Comparative Example 8

Culinary Article in Aluminum with an Outer Enamel Coating on which isPrinted a Hyper-Realistic Decoration in Continuous Tones at the Base.

Based on an aluminum disk, a press makes it possible to obtain a bowl 2in the shape of a frying pan (flat base with skirt such as illustratedon FIGS. 1 and 2).

This bowl 2 is degreased beforehand in an alkaline solution.

The barbotine B1 is applied by spraying on the outer side. In order toobtain an enamel coating this enamel coating is steamed during 15minutes at 560° C.

After cooling, an organic acrylic sub-layer of composition similar tothat of Korean application KR2007/0117247 and the decoration is achievedby means of a reactive ink that is protected by a finishing layer.

After curing at 250° C., a hyper-realistic decoration that does notadhere to the enamel is obtained.

After three passages in the dish-washer, the decoration has entirelydisappeared.

Comparative Example 9

Culinary Article in Aluminum with an Outer Enamel Coating on which isPrinted a Hyper-Realistic Decoration in Continuous Tones at the Base.

Based on an aluminum disk, a press makes it possible to obtain a bowl 2in the shape of a frying pan (flat base with skirt such as illustratedon FIGS. 1 and 2).

This bowl 2 is degreased beforehand in an alkaline solution thensatin-finished in order to give a white-colored homogenous surface.

An organic acrylic sub-layer is applied on the outer side by sprayingsuch as described in Korean patent KR2007/0117247 and the decoration isachieved by means of a reactive ink that is protected by a barbotine B2.This enamel coating is steamed during 15 minutes at 560° C. in order toobtain an enamel coating. After cooling, it is noticed that thedecoration has entirely disappeared by combustion and that the enamelshows an unappealing brown tint.

Comparative Example 10

Culinary Article in Aluminum with an Outer PTFE Coating on which isPrinted a Hyper-Realistic Decoration at the Base.

An aluminum disk is treated beforehand in a chemical or a mechanicalmanner such as to bring a surface roughness allowing for good adhesion.

The white screen printing paste PS1 is applied by screen printing on theentirety of one of the sides in order to obtain a white non cured PTFEcoating layer 3. A drying step at 200° C. makes it possible to obtainthe sub-layer 3.

On this sub-layer is deposited a transparent organic receiving layer ofink such as described in Korean patent KR 2007/0117247, involving athinner and a hardener of organic nature in order to allow for a goodadhesion of the projected ink.

After the ink jet printing of the patterns on the receiving layer, aprotective coating layer PS2 is applied on the printed patterns.

The disk then undergoes a curing at a temperature below 300° C. thenstamped such as to obtain a bowl 2 in the shape of a frying pan (flatbase with skirt such as illustrated on FIGS. 1 and 2).

It is then obtained a culinary article whereof the PTFE coating does nothave the characteristics of an even PTFE coating: bad cohesion of thefilm, no anti-adhesion or chemical resistance. The curing temperaturebelow 300° C. is not sufficient to allow for a good sintering of thePTFE particles.

Comparative Example 11

Culinary Article in Aluminum with an Outer PTFE Coating on which isPrinted a Hyper-Realistic Decoration at the Base.

An aluminum disk is treated beforehand in a chemical or a mechanicalmanner such as to bring a surface roughness allowing for good adhesion.

The white screen printing paste PS1 is applied by screen printing on theentirety of one of the sides in order to obtain a white non cured PTFEcoating layer 3. A drying step at 200° C. makes it possible to obtainthe sub-layer 3.

On this sub-layer is deposited a transparent organic receiving layer ofthe ink such as described in Korean patent KR 2007/0117247, involving athinner and a hardener of organic nature in order to allow for a goodadhesion of the projected ink.

After ink jet printing the patterns on the receiving layer, a protectivecoating layer PS2 is applied on the printed patterns.

The disk then undergoes a curing at a temperature of 420° C. during 10minutes then stamped such as to obtain a bowl 2 in the shape of a fryingpan (flat base with skirt such as illustrated on FIGS. 1 and 2).

After cooling, it is noticed that the PTFE coating has an unappealingbrown tint: the organic receiving layer has been totally damaged bycombustion and the degradation components conceal the decoration.

1. A heating article comprising a substrate having two opposite sides,wherein one of the sides is at least opaque, and a heat-stable coatingarranged on said opaque side, wherein said heat-stable coating comprisesan at least a two-color decoration in continuous tones having the formof one of a continuous or discontinuous layer, and in that said articlehas undergone a curing at a temperature higher than 300° C.
 2. Theheating article according to claim 1, wherein the decoration is arrangedon an opaque sub-layer, which covers one of the sides of said substrate.3. The heating article according to claim 2, wherein the decorationcontains no binders.
 4. The heating article according to claim 1,wherein the heat-stable coating further comprises a continuous andtransparent finishing layer arranged on the decoration.
 5. The heatingarticle according to claim 2, wherein the heat-stable coating furthercomprises a continuous finishing layer arranged between one of thesubstrate or the sub-layer and the decoration.
 6. The heating articleaccording to claim 1, wherein the decoration comprises at least aheat-stable binder that is compatible with the substrate and/or, withthe sub-layer and/or the finishing layer.
 7. The heating articleaccording to claim 6, wherein the heat-stable binder of the decorationis chosen among enamels, fluorocarbon resins (alone or in combination),inorganic polymers or organic-inorganic hybrids synthesized by sol-gelprocess, silicones, silicon-polyesters, polyimids, polyphenylene sulfide(PPS), ethylene sulphide polymer (PES), polyetheretherketones (PEEK),polyetherketones (PEK), polyamids-imids (PAT), silicones,fluorosilicones, polybenzimidazoles (PBI).
 8. The heating articleaccording to claim 1, wherein the decoration comprises at least twodifferent color compounds chosen among heat-stable pigments, metalsalts, semi-conductive thermochromic pigments and combinations thereof.9. The heating article according to claim 1, wherein the decoration isat least four-colors.
 10. The heating article according to claim 1,wherein the support is of a material chosen among metals, glass,ceramics and plastic materials.
 11. The heating article according toclaim 10, wherein the support is a metal of one of an aluminum oraluminum alloy having a polished, brushed, microbeaded or sanded surfacefinish, or of treated chemically, polished, brushed or microbeadedstainless steel, or of cast aluminum, titanium or of polished or beatencopper.
 12. The heating article according to claim 10, wherein thesupport is in cast iron.
 13. The heating article according to claim 1,wherein the heating article constitutes a culinary article whereof oneof the opposite sides is a concave inner side intended to be arranged ona food contacting side of said culinary article, and wherein a second ofsaid opposite sides is an outer convex side intended to be arrangedtowards a heat source.
 14. The heating article according to claim 1,wherein the decoration is in the form of one of a continuous ordiscontinuous layer arranged on an inner side of the article.
 15. Theheating article according to claim 14, wherein the decoration containsno binders.
 16. The heating article according to claim 14, wherein thedecoration comprises a heat-stable binder chosen among fluorocarbonresins, inorganic polymers or organic-inorganic hybrids synthesized bysol-gel process, polyphenylene sulfide (PPS), ethylene sulphide polymer(PES), polyetheretherketones (PEEK), polyetherketones (PEK),polyamids-imids (PAI), polybenzimidazoles (PBI).
 17. The heating articleaccording to claim 1, wherein the decoration is in the form of one of acontinuous or discontinuous layer arranged on an outer side of thearticle.
 18. The heating article according to claim 17, wherein thedecoration contains no binders.
 19. The heating article according toclaim 17, wherein the heat-stable binder of the decoration is chosenamong enamels, fluorocarbon resins, inorganic polymers ororganic-inorganic hybrids synthesized by sol-gel process, silicones,silicone-polyesters, polyimids, polyphenylene sulfide (PPS), ethylenesulphide polymer (PES), polyetheretherketones (PEEK), polyetherketones(PEK), polyamids-imids (PAI), silicones, fluorosilicones,polybenzimidazoles (PBI).
 20. A method for manufacturing a heatingarticle including the following steps: a) providing of a substratecomprising two opposite sides, wherein one of the sides is at leastopaque; b) applying a heat-stable coating on said opaque side, whichcomprises the following steps: b1) a step of applying on said opaqueside a composition of decoration, to form a moist layer of decorationcovering at least partially said opaque side; b2) a heat treatment ofsolidifying said moist layer of decoration, to form a decoration havingthe form of one of a continuous or discontinuous layer covering at leastpartially said opaque side, wherein the composition of the layer ofdecoration comprises at least two different color components and isapplied by ink jet printing, and wherein the heat treatment ofsolidifying the moist layer of decoration is achieved at a temperatureequal to or higher than 300° C.
 21. The method according to claim 20,wherein one of the sides of the substrate is at least partially coveredby a continuous opaque sub-layer.
 22. The method according to claim 21,wherein the composition of the decoration contains no binders.
 23. Themethod according to claim 20, wherein the method further comprises astep of providing a finishing layer, comprising the further steps ofapplying a continuous transparent finishing composition on the layer ofmoist decoration obtained following step b1), prior to the heattreatment b2) of solidification.
 24. The method according to claim 21,wherein the method further comprises a step of providing a finishinglayer comprising the further step of applying of a continuous finishinglayer composition, prior to the realization b1) of the layer ofdecoration.
 25. The method according to claim 20, wherein the decorationcomposition comprises a heat-stable binder.
 26. The method according toclaim 25, wherein the heat-stable binder of the decoration is chosenamong enamels, fluorocarbon resins, inorganic polymers ororganic-inorganic hybrids synthesized by sol-gel process, siliconelacquers, in silicon-polyester or in polyimid.
 27. The method accordingto claim 20, wherein the decoration comprises at least two differentcolor components that are chosen among heat-stable pigments, metalsalts, semi-conductive thermochromic pigments and combinations thereof.28. The method according to claim 27, wherein the decoration is at leastfour-colors.
 29. The method according to claim 28, wherein the at leastfour-colors decoration is hexachrome.
 30. The heating article accordingto claim 1, wherein the at least four-colors decoration is hexachrome.